Prince William has got into Cambridge because he's royal, not because he's posh and rich

That may seem like a minor distinction but, in fact, it's an enormous and important one.

Cambridge undergraduates have been attacking the decision to let Prince William into the university to do a tailored agriculture course. And they're right – it is essentially unfair that, with his average A-Level results, he should just breeze in to one of the best universities in the world. He is hardly a brilliant student. I was once told by a friend who'd met him, 'In real life, he'd be hard-pressed to get a job at Foxtons.'

We indulge the Royal Family – particularly the monarch and direct heirs to the throne – in all sorts of ways that are objectively unfair. The palaces, the vast, spreading acres, the constitutional powers, the deference, the bowing and curtseying… It is all not only unfair but pretty silly if you look at it with pure, cold logic. Why should you get all these things purely as a result of who your parents are?

If you follow that utterly logical line all the way through, then it makes sense to get rid of the lot of them, and create a republic. But life isn't logical and the strange, crazy, utterly illogical thing about our monarchy is that it works.

There's none of the jockeying for power that would come with a presidency. And that in-built popular respect and deference, built up over centuries, means there's a steady source of alternative power when normal political life breaks down – as at the last election, when Gordon Brown, the hermit of Downing Street, desperately tried to cling on even though he'd lost the election. There was no feeling of panic in the streets because we knew that, at the other end of the Mall, there was a secure, sound, utterly sane leader who'd been on the throne for 58 years.

If you accept the usefulness of an efficient monarchy – and there's no reason why you must – then you accept all the unfairness and lack of logic that goes with it. Not just the power and the palaces, but also the access to a top education.

Prince Charles went to Cambridge despite less than satisfactory A-Levels – a B and a C in History and French. His 2.2 in anthropology, archaeology and history is hardly planet-brained stuff. The same went for Edward VIII, who breezed into Magdalen College, Oxford, without the sort of intellectual equipment expected there.

Unfair, certainly. But, if you're going to have a slightly dim monarch on the throne, isn't it better to have one whose grey cells have been topped up at one of our best universities?